Self-Heating Electric Plugger/Syringe Needle For Use In A Root Canal

ABSTRACT

A self-heating electric plugger/syringe needle (10/70) with the conductive element (50) on the external surface of the needle (10/70) is described. The needle (10/70), which can be divided into shank (30) and tip (20) portions, is hollow and is made of an electrically resistive material. A conductive element (50) located on the external surface of the needle runs along the length of its shank (30) and the length of its tip (20). An insulating material (60) located between the conductive element (50) and the external surface of the needle runs along the length of the shank (30). The conductive element (50) contacts the tip (20) of the needle, causing the needle to self-heat when electric current is supplied. A method for filling a root canal using the self-heating electric plugger/syringe needle (10/70) is also described.

BACKGROUND OF THE INVENTION

This invention relates to dental implements and, more particularly todental implements which are particularly designed for the filling ofroot canals with sealing materials.

There are several methods of sealing root canal systems, and most ofthem using a rubber-like material called gutta percha. This gutta perchamay be in the form of a tapered cone, which is compacted into the rootcanal with pluggers. Alternatively, the gutta percha may be placed as acoating on an obturating carrier, which is warmed to soften the guttapercha, and deposited in the root canal where the carrier compacts thematerial into the canal space.

Currently, the shapes of filling materials and obturating carriers donot match the tapering shapes of prepared root canals. When thestep-back technique of canal shaping is used, the final shape of thecanal preparation can only be discerned indirectly by the incrementsthat each larger instrument fits further back from the terminus of thecanal, a difficult skill learned only after much experience. As theprepared taper is often obscure to the clinician, it is likewisedifficult to pick an appropriately tapered gutta percha point orobturating carrier with which to seal the canal. If the selectedobturating device or gutta percha point is too tapered, it will bind inthe canal short of the canal's terminus, causing the crucial apical sealto be inadequate and allowing leakage and failure of the endodontictreatment. If the obturating device or gutta percha point is too narrow,little hydraulic pressure will be exerted on the filling material in thecervical two-thirds of the canal during condensation procedures andlateral or accessory canals in that region of the canal may not besealed, again increasing the chance for failure of the endodontictreatment.

While there are many techniques of filling root canals, it is generallyrecognized in the field of endodontics that those methods which warm andsoften the gutta percha filling material, thereby allowing it to bethoroughly compacted into all the nooks and crannies of root canalsystems, are superior to those techniques which do not thermoplasticizethe gutta percha prior to condensation.

Vertical condensation of warm gutta percha is a known technique forwarming and compacting gutta percha in a root canal (see e.g. U.S. Pat.No. 5,406,053). In this technique, an appropriately tapered gutta perchacone is fit and cemented in the prepared root canal, and a flame-heatedor electrically-heated gutta percha heat carrier is used to sear off thegutta percha cone at the orifice level of the canal. Pressing thesoftened gutta percha into the canal with an appropriately sizedvertical condensation plugger initiates the first wave of condensation,filling any lateral canals present in that region in the primary canal.The heat carrier is then reintroduced into the canal in order topenetrate the gutta percha several millimeters (mm), heat the apicalmass, and remove a portion of the apical mass so that the next wave ofcondensation may occur deeper in the root. These heating and compactingcycles continue until the final wave of condensation which endsapproximately five to seven millimeters from the canal terminus.

It generally takes from three to seven waves of condensation to reachthis end point. At the end point, the clinician must either place aretentive post in the coronal canal space or backfill it with guttapercha. Backfilling can be done by heating small pieces of gutta perchaand sequentially packing them into the canal or by syringing alloquatesof pre-heated gutta percha from a gutta percha gun and compacting themwith pluggers. Downpacking with multiple waves of condensation andbackfilling in the manners described require at least seven differentinstruments, fairly extensive training of the clinician and chairsideassistant, and between fifteen and thirty minutes of clinical time.Furthermore, these condensation pluggers and heat carriers lack acorrelating mechanism to match their sizes to the taper of the canalpreparation.

In the preparation of a root canal by removing the pulp and shaping thecanal to the best configuration for receiving filling materials, such asgutta percha, it is extremely important to control the depth ofpenetration of root canal files and to limit the depth of penetration tothe root tip.

Obturation condensation devices, often referred to as pluggers or, ifprovided with heating elements as heat carrier/pluggers, are designedfor the insertion and packing of tapered gutta percha cones into apreviously prepared root canal. For example, U.S. Pat. No. 5,921,775,herein incorporated by reference, describes an endodontic treatmentsystem in which the shaping instruments, irrigation cannulas, fillingimplements, and related materials are designed to safely create specifictapers in root canal preparation. All of the identified implements aredesigned with the same taper, preferably one which is greater than thestandard ISO taper of 0.02 mm of taper/mm of flute length.

When an electric heat plugger is used to downpack or condense thethermo-plasticized gutta percha into the apical and lateral canalspaces, the gutta percha that moves along the side of the plugger isusually removed after the downpack is completed, leaving the coronalcanal space empty. A second obturation device called a gutta perchabackfilling syringe is required to backfill the empty space. Guttapercha backfilling syringe needles are typically made of sterling silveror a silver alloy because heat conduction from the syringe heatingchamber to the end of the syringe needle must be adequate to keep thetemperature of the gutta percha material high enough to remainthermo-plastic along the entire length of the needle to its tip.However, syringe needles made of silver or silver alloys lack theinherent rigidity to be used to condense the thermo-plasticized materialinto the root canal space after they have heated and extruded saidmaterial into the canal space.

As a result, there is a need for a backfilling syringe needle that canconduct heat from the syringe heating chamber to the tip of the needlewhile maintaining sufficient rigidity to pack the warmed gutta perchainto the canal space. There is also a need for a needle that eliminatesthe need to fit tapered gutta percha master cones or carriers into theroot canal and reduces the typical device set of a downpacking electricheat plugger and a gutta percha backfilling syringe into a singledevice.

SUMMARY OF THE INVENTION

A self-heating electric plugger/syringe needle with the conductiveelement on the external surface of the needle is described. The needle,which can be divided into shank and tip portions, is hollow and is madeof an electrically resistive material. A conductive element located onthe external surface of the needle runs along the length of its shankand the length of its tip. An insulating material located between theconductive element and the external surface of the needle runs along thelength of the shank. The conductive element contacts the tip of theneedle, causing the needle to self-heat when electric current issupplied. The conductive element may have a sinusoidal or straight-linepattern. A method for filling a root canal using the self-heatingelectric plugger/syringe needle is also described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an embodiment of a self-heating electricplugger/syringe needle made according to this invention.

FIG. 2 is a top view of the embodiment shown in FIG. 1.

FIG. 3 is an enlarged view of the tip of the embodiment shown in FIG. 1.

FIG. 4 is a side view of an alternative embodiment of a self-heatingelectric plugger/syringe needle made according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIGS. 1-3, the self-heating electric plugger/syringe needle10 can be divided into a shank 30 portion and a tip 20 portion. Theshank 30 may be tapered, with the diameter of the taper increasing asthe distance from the tip 20 increases. The end of the shank 30 oppositethe tip 20 may be connected to a handpiece (not shown) which deliverselectric current to the conductive element 50 as well as providing ahandle for the clinician to manipulate the electric heat plugger/syringeneedle 10. The bore 25 of the needle 10 is hollow. A gutta perchasyringe mechanism is located in the handpiece so as to pre-soften andpush the thermo-plasticized filling material out through the hollowspace 25 inside the plugger/syringe needle 10.

The self-heating electric plugger/syringe needle 10 is made of anelectrically resistive material, preferably stainless steel. Asinusoidal-shaped conductive element 50, also known as a heatingelement, on the external surface of the needle 10 runs along the lengthof its shank 30 and the length of its tip 20. The conductive element 50is separated from the surface of the needle 10 by an insulating material60, which also runs along the length of the shank 30 of the needle 10.However, at the tip 20 of the needle 10, the conductive element 50directly contacts the electrically resistive material of the needle 10(i.e., the tip 20 is non-insulated). The electrically resistive materialacts as a ground to the electric current which, because the electricallyresistive material is more resistive to the current than the insulatingmaterial 60, causes the needle 10 to self-heat.

As shown in FIG. 4, an alternative embodiment of the self-heatingelectric plugger/syringe needle 70 has a shank 30 portion and a tip 20portion. The shank 30 may be tapered, with the diameter of the taperincreasing as the distance from the tip 20 increases. The end of theshank 30 opposite the tip 20 may be connected to a handpiece (not shown)which delivers electric current to the conductive element 50 as well asproviding a handle for the clinician to manipulate the electric heatplugger/syringe needle 70. The bore 25 of the needle 70 is hollow. Agutta percha syringe mechanism is located in the handpiece so as topre-soften and push the thermo-plasticized filling material out throughthe hollow space 25 inside the plugger/syringe needle 70.

The self-heating electric plugger/syringe needle 70 is made of anelectrically resistive material, preferably stainless steel. Aconductive element 50, also known as a heating element, on the externalsurface of the needle 70 runs in a straight line along the length of itsshank 30 and the length of its tip 20. The conductive element 50 isseparated from the surface of the needle 70 by an insulating material60, which also runs along the length of the shank 30 of the needle 70.However, at the tip 20 of the needle 70, the conductive element 50directly contacts the electrically resistive material of the needle 70(i.e., the tip is non-insulated). The electrically resistive materialacts as a ground to the electric current which, because the electricallyresistive material is more resistive to the current than the insulatingmaterial, causes the needle 70 to self-heat.

While self-heating electric plugger/syringe needles have been describedwith a certain degree of particularity, many changes may be made in thecomponents of the needles, the construction and arrangement of thosecomponents, and methods of using the needles without departing from thespirit and scope of this disclosure. The invention, therefore, islimited only by the scope of the attached claims, including the fullrange of equivalency to which each element thereof is entitled.

What is claimed:
 1. A self-heating electric plugger/syringe needle(10/70) comprising: a hollow needle made of an electrically resistivematerial, the needle having a shank (30) portion and a tip (20) portion;a conductive element (50) located on an external surface of the needle(10/70) and running along a length of the shank (30) portion and alength of the tip (20) portion of the needle (10/70); and an insulatingmaterial (60) located between the conductive element (50) and theexternal surface of the needle and running along the length of the shank(30) portion of the needle (10/70), wherein the conductive element (50)contacts the electrically resistive material of the needle (10/70) atthe tip (20) portion, thereby heating the needle (10/70) when electriccurrent is supplied to the conductive element (50).
 2. A needleaccording to claim 1, wherein the conductive element (50) has asinusoidal pattern.
 3. A needle according to claim 1, wherein theconductive element (50) has a straight-line pattern.
 4. A needleaccording to claim 1, wherein the electrically resistive material isstainless steel.
 5. A method for filling a root canal, using aself-heating electric plugger/syringe needle (10/70), wherein aconductive element (50) located on an external surface of the needle(10/70) contacts a tip (30) portion of the needle (10/70) and causes theneedle (10/70) to self-heat when electric current is supplied to theconductive element (50).
 6. A self-heating electric plugger/syringeneedle (10/70) comprising: a conductive element isolated from anelectrically resistive shank portion of the needle (10/70) by aninsulating material (60) wrapped about the shank portion, the conductiveelement extending past an end of the insulating material to contact theelectrically resistive material at an electrically resistive tip (20)portion of the needle.
 7. A needle according to claim 6, wherein theconductive element (50) has a sinusoidal pattern.
 8. A needle accordingto claim 6, wherein the conductive element (50) has a straight-linepattern.
 9. A needle according to claim 6 further comprising theelectrically resistive shank and tip portions being stainless steel.